Xx. Jiang et al., Characterization of the fibre-matrix interfacial structure in carbon fibre-reinforced polycarbosilane-derived SiC matrix composites using STEM/EELS, J MICROSC O, 196, 1999, pp. 203-212
This paper presents a characterization study of the microstructural evoluti
on of various carbon fibre-reinforced polycarbosilane (PCS)-derived SiC mat
rix composites during high temperature heat treatment. Both surface-treated
and untreated carbon fibre reinforcements were investigated. The STEM/EELS
technique was found to be a particularly useful characterization tool. The
results of quantitative EELS linescans have been interpreted in terms of t
he migration of gaseous SiO and CO, produced by the reaction between the sm
all amount of SiO2 and excess carbon within the PCS-derived SiC matrix, fro
m the central matrix region towards the fibre-matrix interfaces, Generally,
the migration of gaseous SiO and CO results in an enrichment of SiO2 at th
e region adjacent to the fibre-matrix interface. However, differing final c
omposite microstructures are formed depending on the strength of the fibre-
matrix bonding, In the case of strong fibre-matrix interfacial bending wher
e few escape channels are present, a distinct Si-C-O layer was identified w
ithin the matrix adjacent to the fibre-matrix interface: both crystalline b
eta-SiC and the segregated Si-O-C phase coexist in this microstructure up t
o at least 1450 degrees C, In the case of weak fibre-matrix bonding this ox
ygen segregated interfacial layer is eventually removed at high enough temp
eratures. The final interfacial microstructure has important consequences f
or the mechanical properties of the composite material.